Prove that $\frac{\sin 70^{\circ }}{\cos 20^{\circ }}+\frac{\text{cosec}20^{\circ }}{\sec 70^{\circ }}-2\cos 70^{\circ }\text{cosec}20^{\circ }=0$

We know that,

$\cos (90-\theta )=\sin \theta$

$\sec (90-\theta )=cosec\theta$

$cosec(\theta )=\frac{1}{\sin \theta }$

$\frac{\sin 70^{\circ }}{\cos (90-70{)}^{\circ }}+\frac{\csc 20^{\circ }}{\sec (90-20{)}^{\circ }}-2\frac{\cos 70^{\circ }}{\sin 20^{\circ }}=0$

$\frac{\sin 70^{\circ }}{\cos (90-70{)}^{\circ }}+\frac{\csc 20^{\circ }}{\sec (90-20{)}^{\circ }}-2\frac{\cos 70^{\circ }}{\sin (90-70^{\circ })}=0$